For example, we switched to purchasing reserved instances up front to try and reduce our monthly bills (albeit at a higher up front cost). But trying to match up Reserved instances with EC2 or Elastic Beanstalk instances that are actually running is a real headache.
Several times, we've been caught with useless reserved instances sitting there not being utilised - because we had shut down a project or similar. Had we been able to see "Oh, we have 10 t1.micro reserved instances, but only 7 are being utilised by active EC2 instances at the moment" then we could easily know that we could provision another 3 t1.micro instances at no extra cost to experiment with something or for a client project. Or we could convert those t1.micro instances to another region or instance type to meet demand elsewhere.
It would also be handy on their billing reports if they delineated or showed the breakdown of the total usage hours against 'on demand' and 'reserved' instances. I know they _sort of_ do that now, but I think it could be better laid out so we can see at a glance whether we are getting best use from our reserved instances.